Better edge cases and exceptions handling for NNS contract about non-native-contracts HOT 2 OPEN

I'd say that semantically it's pretty close to https://github.com/neo-project/proposals/blob/master/nep-11.mediawiki#ownerof-1 (accepts token ID, returns an iterator related to it) for which we have

The parameter tokenId SHOULD be a valid NFT ID (64 or less bytes long). If not, this method SHOULD throw an exception.

specified. So exception itself is likely OK here, at least it follows NEP-11 conventions. But this exception should be meaningful of course, "invalid format" or "invalid conversion" are hard to decipher.

from non-native-contracts.

Just for the record: https://github.com/neo-project/non-native-contracts/pull/25/files#diff-d92adeab89009d989ac782ad3056dc68aee0e88547e4f101f95764030d2f0410R660 contains fix for this particular issue along with a set of other improvements.

from non-native-contracts.